Parabolic dishes are also useful for UHF and Microwave Communication, Satellite Communication, Troposcatter Communication, Radars and similar applications for receiving and/or transmitting radio signals.
A parabolic dish antenna consists of a metallic or metallized paraboloidal reflecting surface, which is supported by a back-up-structure. Radio waves from a distant radio source or a radio transmitter, are reflected by the paraboloidal reflector surface and are concentrated at the focal point of the dish antenna, where they are received by a primary antenna feed and an amplifier unit. Similarly for a transmitting antenna, radio waves from a transmitter are applied to the antenna-feed and are reflected by the parabolic dish to a far away distance.
The reflector surface of the parabolic dish antennas consists of a number of plane or curved panels, made out of metal or metallized sheets or wire mesh, which are supported by a back-up-structure. The reflecting surface, the back-up-structure and a supporting structure for the antenna feed form the main elements of the parabolic dish antenna. The dish antenna is placed on a fixed or a mechanically driven mount which allows its pointing to different directions of the sky.
Conventionally the back-up-structure of the parabolic dish antenna consists of a large number of curved radial trusses made of structural members, which are interconnected using diagonal bracings and circumferential structural members in order to achieve a 3-dimensional paraboloidal shaped back-up structure (see references cited below). Sometimes a 3-dimensional space-frame configuration is used for the radial, circumferential and bracing members of the back-up-structure made of materials such as steel or aluminum and its alloys, or carbon-fibre tubes. The structural members are welded or riveted or bolted or joined together suitably in order to provide rigidity. Typical examples of back-up structure of some parabolic dish antennas using prior art are shown in FIG. 1 in the accompanying drawings.
The sizes and strength of the materials of the structural members of the parabolic dish antennas are chosen for resisting gravitational and wind forces. In particular, it is required that the tensile and compressive stresses in the structural members of the dish antenna should be within the bounds, as per the national or international structural design codes for the specified survival wind velocity. Conventional parabolic dish antennas or reflector antennas are described in the literature such as:
References to Literature
    i) Baars, J. W. M., Brugge, J. F. van der, Casse, J. L., Hamaker, J. P., Sondar, L. H., Visser, J. J. and Willington, K. J. The Synthesis Radio Telescope at Westerbork, Proc. IEEE, Vol. 61, 1258-1266, 1973.    ii) Goldsmith, P. F.,(eds.), “Instrumentation and Techniques for Radio Astronomy: Part-I: Filled Aperture Antennas”, pp. 17-89, IEEE Press, New York, 1988.    iii) Hoemer, van, S., Design of Large steerable Antennas, Astron. J., vol. 72, pp. 35-47, 1967.    iv) Hooghoudt, B. G., The Benelux Cross Antenna, Ann. N.Y. Acad. Sci., vol 116(1), p.13-24, 1964.    v) Love, A. W., Some Highlights in Reflector Antenna Development in “Reflector Antennas”, Love, A. W., ed., IEEE Press, New York, 1978.    vi) Mar J. W. & Libowitz, K (eds.) “Structure Technology for Large Radio and Radar Telescope Systems” MIT Press, Cambridge 1969.    vii) McAlister, K. R., and Lbum, N. F, The Culgoora Radio Heliograph—The Aerials, Proc. Inst. Radio & Electronics Engrs. Australia, vol. 28, pp. 291-297, 1967.    viii) Schneider, K., and Schonbach, W., 25 m Communication Antenna at Raisting, “Design & Construction of Large Steerable Aerials”, pp. 242-246, IEE Conf. Pub. No.21, Inst. Electronic Engineering, UK.    ix) Swarup, G., Ananthakrishnan, S., Kapahi, V. K., Rao, A. P., Subrahmanya, C. R., and Kulkarni, V. K., The Giant Metrewave Radio Telescope, Current Science, vol.60, pp. 95-105, 1991.    U.S. Pat. No. 3,762,207 (Weiser) teaches a method of Fabricating Curved Surface.    U.S. Pat. No. 4,001,836 (Archer) teaches parabolic dish and method of constructing same.    U.S. Pat. No. 4,378,561 also relates to parabolic reflector antenna.    U.S. Pat. No. 4,568,945 (Winegard) teaches satellite dish antenna apparatus.    U.S. Pat. No. 4,710,777 (Halverson) deals with dish antenna structure.    U.S. Pat. No. 4,731,617 (Gray) relates to apparatus and method for making paraboloidal surface.    U.S. Pat. No. 4,860,023 (Halm) teaches parabolic reflector antenna and method of making same.    U.S. Pat. No. 5,446,474 (Wade) deals with redeployable furlable rib reflector.    French Patent 9,203,506 (corresponding to U.S. Ser. No. 08/035,315) (Rits) relates to collapsible Rib Tensioned Surface (CRTS) Reflector for VLBI Applications.
The conventional design of the back-up-structure of parabolic dish antennas as described in the literature becomes quite complex for large diameter parabolic dishes as can be seen from FIG. 1. The conventional design leads to increased weight of the structural members and also requires considerable amount of welding or bolting. Also the required curvature of both the radial and circumferential members is made by rolling or bending in a suitable machine which is labour intensive.